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Re: plant beds for treatment of rinse water from metal sculpture studio




Sounds like you have a pretty complex waste water problem, and should
probably use a few steps to minimize impact. Because you live in a pretty
cool location, your biological treatment (plants) may have to be seasonal,
so you should optimize your physical/chemical treatment options.

Just like in industrial settings your first step should be solids
separation. That is, you should have a primary holding tank to allow the
particles to settle out. Depending on the specific chemical properties of
the VOC's, they will either sorb to the solids, volatilize to the atmosphere
or stay in the water. You may add some granulated carbon (charcoal) or some
clay to the mix to drag out the organic bad guys. Alternatively, set your
buckets out far away from you so you don't have to breath the VOC's.
Organics that are water soluble will break down by bacteria in the
water/soil along your treatment train. Allow the water to settle for several
hours to days. Be careful not to mix too many different kinds of waste, lest
they react and cause more problems. If you know the water is particularly
acidic, you may want to add some baking soda. Because heavy metal chemistry
is really complex, and even more so in the presence of fluctuations in acid
and base, it is hard to predict the effect of further chemical additions.
Just be observant.

The water should then be decanted into the next treatment step. The settling
tank can be drained periodically with the solids dried and disposed of as
hazardous solid waste (another problem).

Secondary treatment often includes some sort of oxygenation step. This can
be spraying the water out like a fountain or some other bubbling, sloshing
and mixing. You could then run the water through some sand, which would act
like a filter to remove any left over particulate. Finally, the water can
run through plants. I would suggest a warm damp area with some hearty weeds,
less clay and more sand and gravel. Myriophyllum species may be good (water
milfoil). Mustards tend to bio-accumulate heavy metals. Other than that, I
would just look for plants that would grow, survive and are not edible. Most
of the biological treatment will be done by bacteria in the soil/root zone.

You may get better advice by contacting someplace like Georgia Tech Dept. of
Environmental Science and Engineering. Check their web site for anyone doing
physical/chemical/biological treatment of heavy metal waste water and send
them your email. This is a cool little problem and may be a good class
project for some aspiring environmental engineers. They may have something
clever to say--maybe not, but it wouldn't hurt.

Good luck, and remember, your little contribution is nothing compared with
the Savannah River Facility in Augusta!

Mindy Vanderford
Research Assistant
University of North Carolina Chapel Hill
Dept. Environmental Science and Engineering
Chapel Hill, NC 27599


----- Original Message -----
From: Catherine Jo Morgan <cjmorgan@hemc.net>
To: permaculture <permaculture@franklin.oit.unc.edu>
Sent: Saturday, October 14, 2000 1:50 PM
Subject: plant beds for treatment of rinse water from metal sculpture studio


> I'm looking for advice on how to use plants to clean rinse water of
> various VOCs like various glycol ethers, also sometimes very alkaline
> metal cleaners, other times acidic zinc/phosphoric acid metal cleaners.
> All the materials are waterbased, and the rinse water has a pretty low
> concentration of the materials.  It seems possible that the right
> selection of plants, in some kind of special treatment area, could clean
> the water from my studio before it reaches groundwater.
>
> I'm a sculptor, making iron and mixed media bowls.  I'm concerned about
> how to treat the rinse water from cleaning the iron and from washing paint
> brushes.  I'm using the least toxic materials I can find.  Even so, there
> are chemicals I use that I'd rather not drink.  My studio is about 35 feet
> uphill from our well.  I have no septic tank, just pour rinse water into
> 5-gallon buckets.  I generate perhaps 2 to 4 gallons of rinse water a day,
> so I could carry it to a water treatment system a hundred feet or more
> from the well - if I had one.
>
> I'm located in the foothills of the Blue Ridge, in northeast Georgia.
> First frost is usually mid-October, last frost usually early to mid-April.
>  The land here is acidic, clay, covered with mostly hardwoods, some pine,
> with light undergrowth.  Not much of the land is cleared, and most of that
> is under the electricity lines.  But if sunshine is necessary, I could
> probably locate the treatment area in a sunny area.  There's just a lot
> more shady woods to choose from.
>
> I'd greatly appreciate information and leads on how to set up such a
> system, what to consider in designing it, what plants to use, etc.  All
> help will be much appreciated.
>
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